(1) Field of the Invention
The present invention relates to clamping mechanisms and particularly to such mechanisms for use in book manufacturing systems. More specifically, this invention is directed to the manufacture of books and especially to the conveying of inner books between work stations of an inner book processing machine. Accordingly, the general objects of the present invention are to provide novel and improved apparatus and methods of such character.
(2) Description of the Prior Art
In the manufacture of a book it is necessary to move the finished or semi-finished inner book between work stations. To this end, inner book processing machines having transport systems including inner book clamps with oppositely disposed clamp jaws, which may be guided along parallel paths, are known in the art. An example of such a prior inner book clamping mechanism may be seen from published German Patent Application No. 2,815,144. In the system of this published German Application one of the clamp jaws, referred to as the outer jaw, is movable horizontally and transversely to the direction of movement of the other or inner jaw. Thus, to achieve the requisite gripping and conveying, drive devices disposed on each side of the clamp are provided on both jaws. These drive devices are in the form of racks and pinions which carry a frame provided with a cam follower. The clamping force for holding the inner book is derived from a pair of springs which are compressed as a result of the movement of the cam roller along a control cam.
Continuing to discuss prior art devices of the type exemplified by German Application No. 2,815,144, a coupling device installed on the clamp plate of the inner clamp jaw is used to hold the clamp device in both the open and closed positions. Devices of the type shown in German Application No. 2,815,144 are comparatively expensive to manufacture as a result of the relatively complicated drive devices employed to impart movement to the outer clamp jaw, the need for the above-mentioned coupling devices and the requirement for a relatively heavy construction. Further, because of the linear characteristics of the clamping force producing springs, the clamping force decreases as the thickness of the inner book being transported decreases. Thus, to insure that the requisite clamping force will be obtained regardless of inner book thickness, the clamp device must be "over-engineered", i.e., must employ relatively large springs and associated force transmission elements.
A further example of a device for clamping and conveying inner books may be seen from published German Application No. 2,110,836. In the system of this application the clamp jaws are guided along parallel paths and the outer clamp jaw supports racks which are displaceable along the longitudinal axis of the inner clamp jaw. These racks engage pinions at the end of a shaft mounted from the inner clamp jaw, this shaft being parallel to the outer jaw. The racks are joined together behind the inner clamp jaw by means of a bow which causes the opening and closing movement of the jaws by cooperation with a cam roller. In the device of published German Application No. 2,110,836 the clamping force is derived from a torsion spring mounted on the shaft which carries the pinions. The torsion spring extends between the shaft and the inner clamp jaw and the degree of tension in the spring is a function of the distance between the clamp jaws. In order to hold the clamp device in the open position, a return locking device in the form of a second coil spring disposed on the pinion gear shaft is employed.
Inner book clamping devices of the type shown in published German Application No. 2,110,836 have the same disadvantages as discussed above with respect to the device of German Application No. 2,815,144.
To summarize the state of the art, it has not previously been possible to easily vary the clamping force of an inner book clamping device to compensate for the thickness of the inner book to be transported. The previous inability to vary clamping force is particularly significant when the book is comprised of certain types of paper, for example smooth paper. The inability to vary clamping force has resulted in thin inner books being gripped with a substantially reduced clamping force when compared to comparatively thick inner books.